1. Field of the Invention
The present invention relates to a method for forming a semiconductor device. More particularly, the present invention relates to a method for patterning a low dielectric layer of a semiconductor device. The method enables better adhesion between a photoresist and a low dielectric (Low-K) insulating layer by removing a hydroxyl group from a surface of the Low-K insulating layer with a beam. Reliability of the device is thereby improved.
2. Discussion of the Related Art
A plurality of devices numbering above 1×109 may be integrated into one fingernail-sized semiconductor chip. Furthermore, the number of devices integrated into one semiconductor chip increases by geometrical progression.
To obtain high-integration and high-speed in a device, it is necessary to develop the structure and material of a semiconductor chip. Thus, an insulating layer of the semiconductor chip may be formed of a low dielectric material, for example, a Low-K insulating layer.
To manufacture a semiconductor device on a semiconductor wafer of a silicon material, it is necessary to provide various processes for manufacturing the semiconductor device. For example, the processes may include a layer formation process, an ion implantation process, photolithography, etc.
Photolithography uses a photoresist, having a property that changes due to a chemical reaction induced by exposure to light. Photolithography may include steps of depositing a film on a substrate, coating a photoresist on the film, selectively exposing the photoresist by UV (ultra-violet) irradiation, developing the exposed photoresist, etching the film using the developed photoresist as a mask, and stripping the photoresist. It is very important to maintain good adhesion between the film formed on the semiconductor wafer and the coated photoresist.
When an insulating layer is formed of a Low-K insulating material, it is even more important to maintain good adhesion between the Low-K insulating layer and the photoresist. However, adhesion between the Low-K insulating layer and the photoresist may deteriorate due to a hydroxyl group formed in the surface of the Low-K insulating layer.
As shown in FIGS. 1A and 1B, the Low-K insulating layer includes a hydroxyl group provided in the form of a silanol group (Si—OH) and a water molecule having a hydrogen bond, wherein the hydroxyl group has a hydrophilic property. The photoresist has a hydrophobic property. As a result, the adhesion between the photoresist and the Low-K insulating layer is poor.
To remove the silanol group (Si—OH) from the surface of the Low-K insulating layer, a thermal treatment of about 1000° C. is conducted for several hours. However, the temperature of about 1000° C. is too high for the process of manufacturing electronic devices.
Accordingly, a dehydroxylation method for solving the problem caused by the hygroscopic property of the Low-K insulating layer has been researched and studied. Typically, a thermal treatment of about 400° C. may be applied to the Low-K insulating layer under a gas atmosphere including an H2 molecule. In another method, the Low-K insulating layer may be made to be hydrophobic by reacting a silicon organic compound, such as HMDS (HexaMethylDiSilazane), with the hydroxyl group.
If the photoresist is coated after applying the dehydroxylation method to the Low-K insulating layer, the adhesion between the Low-K insulating layer and the photoresist may be improved. Accordingly, as the photoresist is uniformly coated, it is possible to improve the efficiency of an exposure process.
A method for patterning a low dielectric (Low-K) insulating layer of a semiconductor device according to the related art will be described with reference to the accompanying drawings.
First, as shown in FIG. 1A, a low dielectric (Low-K) insulating layer 12 is formed on a semiconductor substrate 11. Then, an HMDS process is applied to the Low-K insulating layer 12 so as to improve the adhesion property by removing at least one —OH group from the Low-K insulating layer 12. Next, a bake process is applied to the semiconductor substrate 11 so as to remove moisture or organic solvent from the semiconductor substrate 11.
Referring to FIG. 1B, as H2O is removed, the hydrophilic —OH group is changed into a hydrophobic —O(H3C)3Si group. As a result, the surface of the Low-K insulating layer 12 has a hydrophobic property.
Then, a photoresist is coated on a surface of the semiconductor substrate, 11 including the Low-K insulating layer 12. Then, a bake process is applied to the coated photoresist to remove solvent from the photoresist. Thereafter, an exposure and development process is performed to form a photoresist pattern.
Subsequently, after performing a hard-bake process for the semiconductor substrate having the photoresist pattern, the exposed Low-K insulating layer is selectively etched using the photoresist pattern as a mask.
Then, after stripping the photoresist pattern of the semiconductor substrate from the Low-K insulating layer, a cleaning process is performed, thereby patterning the Low-K insulating layer.
However, the method for patterning the Low-K insulating layer of the semiconductor device according to the related art has the following disadvantages.
When changing the hydrophilic property of the Low-K insulating layer to a hydrophobic property, to improve the adhesion between the Low-K insulating layer and the photoresist, the HMDS process uses an excessive amount of solution. Also, processing time increases due to the HMDS coating and bake processes.
The treatment, which may include using a H2/N2 gas, is performed for the semiconductor substrate at a temperature of about 400° C. Accordingly, the reliability of device is lowered due to the extra thermal budget.